NEEDED: Expert Advice on 76' BB!

[savatreatabvr]

Alright, I'm at my wits end so I'll start off by explaining what the symptoms are and what I've done so far to correct them! Low idle, rough idle and smoked, I adjusted the valves, replaced the plugs & wires, rebuilt the Quad, replaced the vacuum advance and switched it to manifold vacuum instead of ported, replaced all vacuum lines and it STOPPED smoking, Hallelujah but it still idles low, idles rough and now acts like it's running on 7 cylinders! It's still got power so I can imagine what it will be like when it's running right? You guys have already given me some excellent advice to get me to this point but now I'm so close but so far away! Quite frustrating! Oh, sometimes it does idle somewhat normal but no matter what when I put it in gear the idle drops and runs like I just unplugged a plug wire!

[jrcaprai]

Sounds like a Vacuum leak

[savatreatabvr]

Yeah, I've got one but only can here it under acceleration, not at idle! I've sprayed WD40 everywhere with no help!

Originally Posted by jrcaprai

Sounds like a Vacuum leak

[bucannon]

correct me if im wrong but if your intake manifold isnt sealed up right this may be the problem

[79k30dually]

What is the base timing set at? If you close the choke does the idle speed increase or decrease? Looking down the primary bores, at idle is there gas dripping from the ventures? Plug off the pcv hose, with the pcv valve removed, remove the breather from the other valve cover. Plug both holes, breather and pcv, is there vacuuum in the crank case? I'll try to help you find the problem, if you don't understand why a certain procedure just ask, Ron.

[savatreatabvr]

Thank you Ron, got a few issues up front here, I don't have a timing light and there's no choke on the Quadrajet! I haven't looked down the ventures yet or checked the crank case vacuum but I will check those next! If the spark plug gap is to small, could that make it run bad. Reason I ask is I never gapped the new plugs and on the 454 and the gap is 0.45, I know the new plugs were no where near that!

Originally Posted by 79k30dually

What is the base timing set at? If you close the choke does the idle speed increase or decrease? Looking down the primary bores, at idle is there gas dripping from the ventures? Plug off the pcv hose, with the pcv valve removed, remove the breather from the other valve cover. Plug both holes, breather and pcv, is there vacuuum in the crank case? I'll try to help you find the problem, if you don't understand why a certain procedure just ask, Ron.

[wyattglock]

Originally Posted by savatreatabvr

Thank you Ron, got a few issues up front here, I don't have a timing light and there's no choke on the Quadrajet! I haven't looked down the ventures yet or checked the crank case vacuum but I will check those next! If the spark plug gap is to small, could that make it run bad. Reason I ask is I never gapped the new plugs and on the 454 and the gap is 0.45, I know the new plugs were no where near that!

Yes the gap being to small can affect how it runs. It wouldn't hurt to re-gap the plugs and see if that helps. But I also think you have a vacuum issue. One last thing, a decent timing light is probably one of the best tools you can invest in. It will save you more than it costs with the time and parts you don't need to replace.

[INSIDIOUS '86]

are you running a points distributor? i cant see a big hei cap back there

[f.monroe]

If you can hear a vacuum leak and all of the normal places do not reveal it , then look at the brake booster . Maybe pull the hose going to it and plug it. I also think it sounds like a timing issue. My original square body went through many engines and one of the funnest combos I had was a 454/th400/3.73 gear. It pulled great to 5700 rpm and ran very well. Every now and then I would notice it starting to lose power and it also started running like it was dropping cylinders. I found that no matter what I did , my timing would slowly back off. It took it a couple months but it would eventually get to a point that I noticed it badly. I put some more advance in it and it was its old self again. I think you need to get that timing checked.
Frank

[savatreatabvr]

No points, it's a HEI. I'm starting to think a .45 round just left of the thermostat housing would fix ur right up! Then again it'd probably ricochet and I'd end up with a permanent limp!

Originally Posted by INSIDIOUS '86

are you running a points distributor? i cant see a big hei cap back there

[INSIDIOUS '86]

what kind of smoke did it have? you may have a blown head gasket which can cause that of symptom

[RUSHNBOBO]

You said it "idles rough" ....what does it do under acceleration ? run smoother, worse, or the same. This will help diagnose if its a carb or vacuum problem, carb issues or vacuum leaks will very often act differently when the rpm's vary. Vacuum leaks usually don't idle low and rough , if anything it will idle faster and rough, the exception being a gaping hole like if the brake booster hose was removed. When excessive air is being drawn into the engine through the leak, the throttle stop usually will seem to be unresponsive even turned all the way out, this is because the the throttle plates are closed and the engine is drawing most of the air through the leak only.

Also you mentioned it has no vacuum leak at idle but you have one under acceleration, this is very unlikely since there is little or no manifold vacuum under acceleration, when you snap open the throttle the vacuum should drop off to near zero. About the only time you will notice a vacuum leak is at idle or just off idle, if it's really bad; once the plates are open, most of the suction of the engine will go through the path of least resistance (the carb) not the smaller leak. Another clue is "sometimes it idles better," this also is not typical of a vacuum leak, the leak or gap where the vacuum is being drawn through is unlikely going to change while the engine is running.

INSIDIOUS '86...pointed out what color was the smoke ? (very important...)
---white....water vapor, blown head gasket or cracked block or heads
---blue.....oil burning, rings, valve guides
---black....overly rich fuel mixture, stuck float, idle screws out to far, float level off, etc.

Have you tried hooking up a vacuum guage and running the engine through various rpm ranges ? this can diagnose all kinds of problems, especially mechanical by observing the reaction of the needle under different conditions.

[savatreatabvr]

Thanks Rushn for setting me straight with your vacuum leak description, it makes alot of since. Has anyone ever heard of a vacuum leak where the distributor fits into the intake manifold, it's a long shot? I'm pretty sure the smoke was bluish but if that's the case just adjusting the valves wouldn't stop it from smoking, right? Yeah, it does seem to idle somewhat normal from time to time but as soon as I put it in drive it starts chuggin until I accelerate to a steady speed.

Originally Posted by RUSHNBOBO

You said it "idles rough" ....what does it do under acceleration ? run smoother, worse, or the same. This will help diagnose if its a carb or vacuum problem, carb issues or vacuum leaks will very often act differently when the rpm's vary. Vacuum leaks usually don't idle low and rough , if anything it will idle faster and rough, the exception being a gaping hole like if the brake booster hose was removed. When excessive air is being drawn into the engine through the leak, the throttle stop usually will seem to be unresponsive even turned all the way out, this is because the the throttle plates are closed and the engine is drawing most of the air through the leak only.

Also you mentioned it has no vacuum leak at idle but you have one under acceleration, this is very unlikely since there is little or no manifold vacuum under acceleration, when you snap open the throttle the vacuum should drop off to near zero. About the only time you will notice a vacuum leak is at idle or just off idle, if it's really bad; once the plates are open, most of the suction of the engine will go through the path of least resistance (the carb) not the smaller leak. Another clue is "sometimes it idles better," this also is not typical of a vacuum leak, the leak or gap where the vacuum is being drawn through is unlikely going to change while the engine is running.

INSIDIOUS '86...pointed out what color was the smoke ? (very important...)
---white....water vapor, blown head gasket or cracked block or heads
---blue.....oil burning, rings, valve guides
---black....overly rich fuel mixture, stuck float, idle screws out to far, float level off, etc.

Have you tried hooking up a vacuum guage and running the engine through various rpm ranges ? this can diagnose all kinds of problems, especially mechanical by observing the reaction of the needle under different conditions.

[RUSHNBOBO]

Originally Posted by savatreatabvr

Has anyone ever heard of a vacuum leak where the distributor fits into the intake manifold, it's a long shot? I'm pretty sure the smoke was bluish but if that's the case just adjusting the valves wouldn't stop it from smoking, right? Yeah, it does seem to idle somewhat normal from time to time but as soon as I put it in drive it starts chuggin until I accelerate to a steady speed.

The distributor goes through the lifter valley to the camshaft and also drives the oil pump.....but it does not affect the engine vacuum, it is isolated from the intake portion of the manifold, the only thing it can do is leak oil.

Also do you still see the blue smoke at all , if so when ?.....is it all the time ?.....or is it most prevalent in the morning at startup and when getting back on the accelerator after coasting (such as at the bottom of a hill) ? Adjusting the valves would have no affect on oil burning type smoke "blue".

How well does it idle in park or neutral before you shift to drive.....does it sound smooth, or can you hear a slight stumbling or maybe a misfire ?

[savatreatabvr]

That's the thing, before I adjusted the valves it would smoke at idle, like at a long stop light and then leaving the light under normal acceleration it would stumble and leave a cloud. After adjusting the valves it does not smoke at all but still runs rough and I still have to feather the throttle or else it would probably die, nothing like breaking down in the middle of an intersection!

Originally Posted by RUSHNBOBO

The distributor goes through the lifter valley to the camshaft and also drives the oil pump.....but it does not affect the engine vacuum, it is isolated from the intake portion of the manifold, the only thing it can do is leak oil.


Also do you still see the blue smoke at all , if so when ?.....is it all the time ?.....or is it most prevalent in the morning at startup and when getting back on the accelerator after coasting (such as at the bottom of a hill) ? Adjusting the valves would have no affect on oil burning type smoke "blue".

How well does it idle in park or neutral before you shift to drive.....does it sound smooth, or can you hear a slight stumbling or maybe a misfire ?

[INSIDIOUS '86]

Originally Posted by savatreatabvr

That's the thing, before I adjusted the valves it would smoke at idle, like at a long stop light and then leaving the light under normal acceleration it would stumble and leave a cloud. After adjusting the valves it does not smoke at all but still runs rough and I still have to feather the throttle or else it would probably die, nothing like breaking down in the middle of an intersection!

what procedure did you use to adjust the valves?

[savatreatabvr]

The running procedure.

Originally Posted by INSIDIOUS '86

what procedure did you use to adjust the valves?